Check out this "eco-friendly" birdhouse. It's a solar powered bird house that lights up at night. Birds that nest in houses, naturally nest in tree cavities--where it's dark, they want it dark, they do not want a brightly lit perch outside the hole--they actually don't want a perch either. A well made bird house does not have a perch on it. If you watch birds that nest in cavities, the put their feet on the hole and push into the house. Sitting on a perch and turning their head is an awkward position for them.

The light could serve to attract predators. Some predators, like snakes and lizards would come to the light looking for insects attracted to it, and boy, what a delightful surprise to find eggs and chicks to eat.

I always thought the bird feeders that light up at night were silly, but it's decorative and birds aren't using it at night so it doesn't matter. But for nesting birds, this idea appears ill-conceived.